Internal Landforming Processes: Earth Movements, Folding, Faulting, Vulcanicity, and Earthquakes

A comprehensive vocabulary review of Form Two Geography internal landforming processes, covering earth movements, continental drift, plate tectonics, folding, faulting, vulcanicity, and earthquakes.

Earth Movement

Processes operating in the interior of the earth that result in the formation of natural physical features or landforms.

Crustal Earth Movements

The displacement of the earth's crustal rocks brought about by tectonic forces (tension, compression, shear, and gravitational forces) originating and operating in the interior of the earth.

Horizontal (Orogenic) Earth Movements

Movements acting along a horizontal plane within crustal rocks caused by tensional, compressional, and shear forces.

Vertical Earth Movements

Movements that occur along the earth's radius towards the earth's surface or towards its center, causing downwarping, upwarping, or vertical tilting.

Isostasy

The state of balance between the Sial and Sima layers of the earth.

Isostatic Adjustment

The rising of continental masses to restore an upset state of balance between Sial and Sima layers.

Pangea

A single Sialic landmass proposed by the continental drift theory that was surrounded by a massive ocean and later broke apart.

Bandalasa

The huge ocean whose floor was a mass of Sima that originally surrounded the supercontinent Pangea.

Tethys

A narrow ocean that separated Laurasia and Gondwanaland after Pangea broke apart.

Asthenosphere

The molten layer of the earth's mantle upon which crustal tectonic plates float.

Constructive Boundary

An extensional boundary formed where tectonic plates move away from each other and magma fills the space between.

Destructive Boundary

A compressional boundary formed where tectonic plates move toward each other and the materials between them are crushed.

Subduction

The movement where the edge of an oceanic plate slides or passes beneath the edge of another plate into the mantle.

Folding

A process in which crustal rocks are distorted by compressional forces, causing them to bend upwards and downwards.

Escarpment (Folding)

A relatively continuous line of steep slopes facing the same direction, formed when compressional force causes a steep limb on an anticline.

Intermontane Plateau

A fairly level area of elevated land situated between fold mountains.

Faulting

The cracking or fracturing of brittle crustal rocks due to tectonic forces.

Fault Steps

Landforms resembling a staircase or steps of a house formed by a series of fault scarps occurring at different levels.

Tilt Blocks

Fault blocks that have experienced greater uplift on one side, leaving them tilted at the top rather than flat.

Rift Valley

A long, narrow trough bordered by steep escarpments on both sides.

Vulcanicity

The process in which solid, liquid, or gaseous materials are forced out of the interior of the earth into the crust or onto the earth's surface.

Intrusive Vulcanicity

A form of vulcanicity in which molten igneous material intrudes into crustal rocks and cools before reaching the earth's surface.

Extrusive Vulcanicity

A form of vulcanicity where molten igneous materials breach and reach the earth's surface via vents or fissures.

Laccolith

A mushroom-shaped igneous intrusion that lies between the bedding planes of country rock.

Sill

A horizontal or concordant sheet of igneous intrusion that lies along the bedding plane of rock strata.

Dike

A wall-like igneous intrusion that cuts across the bedding planes of rock strata.

Acidic Lava Dome

A steep, dome-shaped volcanic hill formed from viscous acidic lava, having a narrow base and steep slopes.

Basic Dome (Shield Dome)

A low-lying volcanic hill characterized by gentle slopes, a broad base, and composed of basic lava.

Composite Volcano

A volcano constructed of alternating layers of solidified lava, pyroclasts, and conelets built over repeated eruptions.

Plug Dome

A column of highly viscous lava that sticks upright above the ground at a volcanic vent.

Volcanic Plug

A rigid stump of rock formed when magma solidifies inside a volcanic vent, later exposed at the surface by denudation.

Crater

A funnel-shaped depression found on the summit of a volcano.

Caldera

A very large basin-shaped depression located on the summit of a volcano, formed by violent explosions, subsidence, or outward collapse.

Fumaroles

Vents or openings in the earth's crust that emit hot gases generated by subterranean chemical reactions and heated magma.

Hot Spring

A surface geothermal feature where hot or warm water is quietly emitted from the ground.

Geyser

A geothermal feature characterized by an intermittent and violent ejection of superheated water and steam from the ground.

Earthquake

A sudden and rapid movement or shaking of the earth's crust caused by passing shock waves.

Seismic Focus

The originating point or source location of an earthquake within the earth's crust.

Epicenter

The point on the earth's surface directly vertically above the seismic focus where earthquake shock waves are felt first.

Seismogram

A graph-like instrument record displaying the vibrations and shock waves generated by an earthquake.

Macaulay Scale

The scale referenced in the lecture used to measure the intensity of an earthquake.

Richter Scale

The standard logarithmic scale used to measure the total energy released or magnitude of an earthquake.